> For others, it can be hours of crying, even to the point of vomiting (common enough to be a frequent topic of conversation on sleep-training forums and addressed by baby sleep books including Ferber's
The article also includes a reference to 2-3 hours.
Everyone thinks that the position even 1% different from what they adopted is abhorrent.
https://www.attachmentparenting.org/ensure-safe-sleep-physic...
"Research shows us that an infant is not neurologically or developmentally capable of calming or soothing himself to sleep in a way that is healthy. The part of the brain that helps with self-soothing isn't well developed until the child is two and a half to three years of age. Until that time, a child depends on his parents to help him calm down and learn to regulate his intense feelings."
Edit to add: attachmentparenting.org is not an objective arbiter of the research on whether or not the dogmas of attachment parenting are correct! They have a dog in this fight...